As an image sensor used for a camera device, a CCD sensor and a CMOS sensor are known. However, these solid state imaging devices have dynamic ranges of luminance narrower than a dynamic range of brightness of an actual object and therefore easily cause a drop in image quality such as so-called “over exposure” and “under exposure”. Therefore, imaging control of the sensor and signal processing of the sensor output obtained as a result of the imaging sensor are used to expand the dynamic range of the imaging signal.
As these kind methods, a method is known of forming pixels in advance while classifying the pixels to ones having a high sensitivity and ones having a low sensitivity in accordance with the type of pixel filter etc., determining which signals of those pixels to mainly use in accordance with the luminance of the image by signal processing, and using these pixels to form a single image. Further, another method is known of capturing an image of one picture (one frame or one field) one time, but controlling a reset level of signal charges at the time of output of the signal charge, and expanding the dynamic range of the imaging signal so that the amount of overflow becomes different in accordance with the brightness of the picture (specifically, the amount of signal charges from each pixel) (see for example Patent Document 1). Further, a method is known of capturing images of a single picture a plurality of times at different imaging times and mixing these images to generate an image having a wide dynamic range by signal processing (see for example Patent Document 2).
Patent Document 1: Japanese Patent Publication (A) No. 10-248035
Patent Document 2: Japanese Patent Publication (A) No. 06-141229